If you wish to convert to Linux

A friend of mine has just had his computer infected by a virus. Since he would most likely have to reinstall his OS anyway, this would be a good chance to switch if he wishes to. So, I've come up with a comprehensive list of things to do if you intend to switch over to a dual-OS environment. FYI, for a comprehensive list of all known Linux virii, refer to this list (notice how short it is).

1 BACKUP YOUR DATA
I cannot stress this enough. As with any other OS install, you will want to backup any and all your essential data first. This should include any document files you have, your music collection, your source code library and anything else that you would consider essential. Also, you should back it up onto a suitable medium such as an external hard drive that is unencrypted or a DVD

2 DOWNLOAD LINUX
As your computer is still working, it would be a good idea to download and burn a Linux installer for your computer. A lot of people recommend using Ubuntu for people new to Linux. It is supposed to be distro that caters to people who switch over. Personally, I recommend Slackware as it allows you to properly learn how to use Linux, and not learn how to use Ubuntu. Fortunately for everyone, Ubuntu had just released their latest version two days ago. So, you can be assured of getting the latest and greatest on it. If you're not in a rush, feel free to order a free CD from Canonical. I can assure you that they actually mail it out to you.

3 INSTALL LINUX
How you do this will depend entirely on the distro you selected. However, the general steps would require you to pop in the CD/DVD into your computer and reboot your machine. It should start up from the CD/DVD and take you into the installation sequence. Then, choose to wipeout your whole computer and start from scratch. There isn't a real need to repartition for Windows as we will do it through a different method.

4 START LINUX
Once you've installed Linux, boot it up and make sure that everything works properly. For Ubuntu, all your hardware should be detected and configure automagically during installation.

5 INSTALL WINDOWS
Assuming that you need to run Windows as well, in the old days, you would need to install a dual-boot system. This was a rather tricky thing to do with Windows 2000 or later. These days, there is another alternative, through virtualisation. VMWare is available for free download. It is one of the more robust virtualisation solutions out there.

Now to answer some of his specific questions:
1 PDF READER
You can install the latest Adobe Acrobat Reader for Linux or you could choose to use one of the alternative Linux readers available. I personally use KPDF because it's faster and has better cut-n-paste features.

2 MUSIC PLAYER
There isn't an iTunes for Linux, but there are many alternatives. I use Amarok, which is much better than iTunes for managing a music library (I'm saying this with a straight face). As for the M4A files, it's supported by a whole bunch of players including Amarok.

3 COMMUNICATION
Skype has a Linux version for download. There are many alternative instant messengers that can be used to communicate with MSN. I personally use Kopete because it integrates well with my other PIM and email programmes.

4 USB HARDWARE
Camera: will most certainly work. Refer to this list for the cameras. If it's not on the list, it is probably recognised as an external drive rather than a camera. That means that it'll still work.
Palm: If it's running PalmOS, it will certainly work. If it's running a PocketPC, according to this article, it's fairly straightforward as well.
Sound: 100% guaranteed to work. You may need to turn the mixer up the first time you boot up. I always forget this. The mixer defaults to mute after first install.
Webcam: I've never used a webcam before. So, I'm not too sure. But according to this list, it shouldn't have much problems either.

5 GAMES
Warcraft 3: 100% guaranteed to run under WINE with no performance loss using OpenGL.
C&C3: According to this it works and is totally playable. Nuff said.

6 ANTI-VIRUS
What anti virus? "Virus scanners are available for Linux systems in order to scan for Windows viruses and protect downstream Email users with Windows systems." - Wikipedia.

I rest my case. Any other questions, please feel free to use Google or Wikipedia. They're a great source of information on these things. There are many guides and forums that you can refer to during the switch. Good Luck!